An image forming apparatus that includes an intermediate transfer member is a hitherto known example of an electrophotographic image forming apparatus. In an existing image forming apparatus, a voltage is applied from a voltage power supply to a primary transfer member arranged opposite a photosensitive drum with an intermediate transfer member interposed therebetween, and a primary transfer potential is thereby generated at a primary transfer portion of the intermediate transfer member which comes into contact with the photosensitive drum. Then, a toner image formed on the surface of the photosensitive drum serving as an image carrier is primary-transferred onto the intermediate transfer member by a potential difference produced between the photosensitive drum and the intermediate transfer member (primary transfer process). Subsequently, for each color toner, this primary transfer process is repeatedly performed, and toner images of a plurality of colors are formed on a surface of the intermediate transfer member. Then, as a secondary transfer process, the toner images of the plurality of colors formed on the surface of the intermediate transfer member are secondary-transferred in one go onto a surface of a recording material, such as paper, by applying a voltage to a secondary transfer member. The toner images transferred in one go are subsequently fixed onto the recording material by a fixing unit.
PTL 1 discloses a structure in which a belt is used as an intermediate transfer member (hereinafter referred to as an intermediate transfer belt), a transfer power supply dedicated to primary transfer is connected to a stretching member or a primary transfer member that stretches an inner periphery of the intermediate transfer belt, and primary transfer is performed by passing a current in the circumferential direction of the intermediate transfer belt.
Here, the circumferential direction of the intermediate transfer belt is the direction of rotational movement of the intermediate transfer belt. PTL 1 discloses a structure in which primary transfer potentials are produced at primary transfer portions by divided voltages generated when a current supplied from a member (the stretching member or the primary transfer member) to which the power supply is connected flows in the circumferential direction of the intermediate transfer belt.